Bausager
3a53b6ebf7
done single-threded 1d interpolations; linear, rational, cubic spline, polynomial and barycentric. Still not done test functions yet. Still missing multi-core options.
76 lines
1.8 KiB
C++
76 lines
1.8 KiB
C++
#pragma once
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#include "./numerics/interpolation1d_base.h"
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#include "./numerics/abs.h"
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#include "./utils/vector.h"
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namespace numerics{
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template <typename T>
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struct interp_polynomial : Base_interp<T> {
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using Base = Base_interp<T>;
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// bring base data members into scope (or use this->xx / this->yy below)
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using Base::xx;
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using Base::yy;
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using Base::mm;
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T dy;
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interp_polynomial(const utils::Vector<T> &xv, const utils::Vector<T> &yv, uint64_t m)
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: Base_interp<T>(xv, &yv[0], m), dy(T{0}){}
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T rawinterp(int64_t jl, T x) override{
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int64_t ns=0;
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T y, den, dif, dift, ho, hp, w;
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const T *xa = &xx[jl], *ya = &yy[jl];
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utils::Vector<T> c(mm,0), d(mm,0);
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dif = numerics::abs(x-xa[0]);
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for (int64_t i = 0; i < mm; ++i){ // Here we find the index ns of the closest table entry,
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dift = numerics::abs(x-xa[i]);
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if (dift < dif){
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ns = i;
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dif=dift;
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}
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c[i]=ya[i]; // and initialize the tableau of c’s and d’s.
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d[i]=ya[i];
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}
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y = ya[ns]; // This is the initial approximation to y.
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ns -= 1;
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for (int64_t m = 1; m < mm; ++m){ // For each column of the tableau,
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for (int64_t i = 0; i < mm-m; ++i){ // we loop over the current c’s and d’s and update them.
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ho = xa[i]-x;
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hp = xa[i+m]-x;
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w = c[i+1]-d[i];
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den = ho-hp;
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if (den == T{0.0}){
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throw std::invalid_argument("interp_polynomial error"); // This error can occur only if two input xa’s are (to within roundoff identical.
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}
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den = w/den; // Here the c’s and d’s are updated.
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d[i] = hp*den;
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c[i] = ho*den;
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}
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bool take_left = 2 * (ns + 1) < (mm - m);
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if (take_left) {
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dy = c[ns + 1];
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y += dy;
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} else {
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dy = d[ns];
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y += dy;
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ns -= 1;
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}
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}
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return y;
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}
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};
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} // namespace numerics
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